The efficiency of leaf photosynthesis has been measured using a technique called chlorophyll fluorescence. It is not widely known that in addition to leaf photosynthesis the bark of certain “smooth barked” trees can photosynthesize. In this paper we use chlorophyll fluorescence to measure the efficiency of bark photosynthesis. In this way we are able to compare the amount of wood decay in a tree with bark photosynthetic efficiency using chlorophyll fluorescence. The link between bark photosynthesis and wood decay discovered in this work has not been explored before.